Effects of source rocks, soil features and climate on natural gamma radioactivity in the Crati valley (Calabria, Southern Italy).

radioactivityin terms of spatial and temporal variability, was aimed to characterize the background levels ofnatural radionuclides in soil and rock in the urban and peri-urban soil of a southern Italy area; to quantify their variations due to radionuclide bearing minerals and soil properties, taking into account nature andextent of seasonality influence. Its main novelty is taking into account the effect of climate in controlling natural gamma radioactivity as well as analysing soil radioactivity in terms of soil properties and pedogenetic processes.In different bedrocks and soils, activities of natural radionuclides (238U, 232Th 4 K) and total radioactivitywere measured at 181 locations by means of scintillation gamma-ray spectrometry. In addition, selected rocks samples were collected and analysed, using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS) and an X-Ray Powder Diffraction (XRPD), to assess the mainsources of radionuclides. The natural-gamma background is intimately related to differing petrologicfeatures of crystalline source rocks and to peculiar pedogenetic features and processes. The radioactivitysurvey was conducted during two different seasons with marked changes in the main climatic characteristics,namely dry summer and moist winter, to evaluate possible effects of seasonal climatic variations and soil properties on radioactivity measurements. Seasonal variations of radionuclides activities show their peak values in summer. The activities of 238U, 232Th and 4 K exhibit a positive correlation with the air temperature and are negatively correlated with precipitations.